Exploring effective electrocatalysts
for oxygen evolution reaction
(OER) is a crucial requirement of many energy storage and transformation
systems, involving fuel cells, water electrolysis, and metal–air
batteries. Transition-metal oxides (TMOs) have attracted much attention
to OER catalysts because of their earth abundance, tunable electronic
properties, and so forth. Defect engineering is a general and the
most important strategy to tune the electronic structure and control
size, and thus improve their intrinsic activities. Herein, OER performance
on spinel CuCo2O4 was greatly enhanced through
cation substitution and size reduction. Ce-substituted spinel CuCeδCo2−δOx (δ = 0.45, 0.5 and 0.55) nanoparticles in the quantum
dot scale (2–8 nm) were synthesized using a simple and facile
phase-transfer coprecipitation strategy. The as-prepared samples were
highly dispersed and have displayed a low overpotential of 294 mV
at 10 mA·cm–2 and a Tafel slope of 57.5 mV·dec–1, which outperform commercial RuO2 and
the most high-performance analogous catalysts reported. The experimental
and calculated results all confirm that Ce substitution with an appropriate
content can produce rich oxygen vacancies, tune intermediate absorption,
consequently lower the energy barrier of the determining step, and
greatly enhance the OER activity of the catalysts. This work not only
provides advanced OER catalysts but also opens a general avenue to
understand the structure–activity relationship of pristine
TMO catalysts deeply in the quantum dot scale and the rational design
of more efficient OER catalysts.